Question

if there are 2040 seats in a section of a stadium, 20 seats in the first row, and 4 more seats in each row, how many rows are there?

Answer 1

Nth term: 16+4n
2040=16+4n
Subtract 16 from both sides
2024=4n
Divide by 4
506=n
506 rows

Answer 2

2040 = n/2(20+(n-1)4)

4080 = n(20+4n-4)

4080= 20n +4n^2 -4n

1020 = 4n + n^2

n^2 +4n -1020 =0

use common formula (can't write out so just look at answers. sorry)

which gives answers of n=-34 and n=30. since n can only be positive, n=30 so there are 30 rows. I liked that challenge